Gallium nitride (GaN) single crystals have a wide direct bandgap (3.4 eV at 300K) and have been disclosed for use for blue light emitting diodes and laser diodes. See Maruska, H. P., et al., Appl. Phys. Lett. 15, 327-329 (1969); Morkoc, H., et al., Science 267, 51-55 (1995); and Morkoc, H., et al., J. Appl. Phys. 76, 1363-1398 (1994).
GaN dissociates before it sublimes or melts. Therefore single crystals of GaN cannot be prepared from a melt.
GaN single crystals have been reported as having been prepared by the reaction of Ga and N.sub.2 under N.sub.2 pressure of 8,000 to 17,000 atmospheres at temperatures ranging from 1,300.degree. to 1,600.degree. C. GaN single crystals have also been reported as having been grown at temperatures above 1,100.degree. C. in vapor phase using NH.sub.3 as a source of nitrogen. GaN crystals have also been reported as having been prepared by flowing a mixture of NH.sub.3 and H.sub.2 over a Ga melt at 900.degree. to 1,000.degree. C. The conditions for these methods are economically unsound.